Testing arrangement for circuit interrupting devices



Oct. 27, 1953 R. c. VAN SICKLE 2,557,354

TESTING ARRANGEMENT FOR CIRCUIT INTERR'UPTING DEvIcEs 2 Sheets-Sheet 1 Filed July 22, 1950 Generated Voltage i m l I i I I I I i I Are Voltage 0 I WITNESSES:

INVENTOR Roswell C. Van Sickle. BY'R/ f ATTORNE za/e M Oct. 27, 1953 Q VAN s c LE 2,657,354

TESTING ARRANGEMENT FORIJIRCUIT INTERRUPTING DEVICES 2 Sheets-Sheet 2 Filed July 22, 1950 Arc Voltage Generated Voltage l WITNESSES: 4 M Zflf M ATTORN Patented Oct. 27, 1953 v mean an.

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eonditionsi across the test-breaker its e fdfictien of time for one-set ofonditions; and

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3 load circuit of the auto-transformer I3, including the test breaker I9.

Actuation of the overload relay 22 causes substantially simultaneous opening of the test breaker I9 and the auxiliary breaker 2| by means hereinafter more fully described.

An electrically actuated latch device 23 is provided latching the test breaker I9 in its closed position, the latch 23 engaging a nose 24 associated with the operating rod 25 of the test breaker I9. Similarly, an electrically actuated latch device 26 engages a nose 21 secured to and movable with the operatin rod 28 of the auxiliary breaker 2 I. Latches 23, 26 are respectively urged by compression Springs 29, 36 to their latching positions. Substantially simultaneous release of the latches 23, 26 is eifected by energization of their operating coils 3|, 32 through the respective front contacts 33, 34 of the breakers 2|, I9, this being effected by closure of the front contacts 35 of the overload relay 22.

The breakers I9, 2| in their open circuit position, as shown in the drawings, are moved substantially simultaneously to the closed circuit position by the depressing of a push button 36. The electrical circuit for energizing the operating coils 31, 38 of the respective breakers I9, 2| not only includes the push button 36, but also back contacts 39, 40, respectively, of breakers 2|, I9.

The sequence of the testing operation is as follows: First, the test breaker l9 and the auxiliary breaker 2| are closed by depressing the push button 36. Closing of these two breakers automatically opens their coil circuits through the back contacts 39, 43, the latching devices 23, 23 maintaining them in their closed position.

Second, the closing switch 4 is closed by depressing the push button I. Closing the push button 'I energizes the operating coil 6 to close the closing switch 4. The closing of the switch 4 automatically deenergizes the operating coil 6 through the back contacts 8, and permits the latch device 9 to hold the switch 4 in the closed position.

The closing of the closing switch 4 energizes the transformer 2 and also the auto-transformer I8, thereby sending a short circuit current through both interrupting devices I9, 2|. It will be noticed that the short circuit current iT through the test breaker I9 is equal to the current through the secondary winding 29, is, plus the current passing through the primary winding 4| of the auto-transformer I8, 2'

Third, the overload relay 22 operates from the overload current passing through the load circuit of the auto-transformer I3 including the test breaker I9, and hence energizes the trip coils 3|, 32 of the latch devices 23, 26. This causes substantially simultaneous opening of the test breaker I9 and the auxiliary breaker 2|.

Fourth, after the contacts have separated a specific distance the interrupting devices I9 and 2| are ready to extinguish the arcs and both will extinguish the arcs at the next current zero.

Fifth, the recovery voltage Ep appears across both the test breaker I9 and the auxiliary breaker 2|. Since the circuit is opened at switch 2!, the auto-transformer I8 cannot function as an auto-transformer, but does function as a reactor between the power sources I and 2 and the test breaker I9. It acts as such during the recovery transient while the potential across the terminals of the test breaker I9 changes from the arc voltage to the voltage Ep. It will be noted that the auxiliary breaker 2| has carried less current than has flowed through the test breaker I9, it being observed that Sixth, the voltage may be removed from the test arrangement by opening the closing switch 4, that is, by depressing the push button I4.

' Fig. 2 collectively shows a group of three curves A, B, and C. Curve A indicatesv the current flow, I, through the test breaker I9. The current flow I lags the generated voltage wave, as represented in curve B, by 90, as indicated in Fig. 2. Assuming that the contacts of the test breaker I9 and the auxiliary breaker 2| open at, say the time T1 of Fig. 2, the voltage across the breaker contacts of the test interrupter 9 will show arc voltage as indicated in curve C in Fig. 2.

At the time T2 the contacts of the test breaker I9 and the auxiliary breaker 2| have opened sufficiently far to interrupt the circuit. Thus, the current wave I, represented by curve A comes to zero at the point 42, the generated voltage at this time being a maximum, as at 43. The voltage across the breaker attempts to assume the value of the alternating voltage E but overshoots, as indicated in curve C, in an oscillatory manner, until at the point 44 it settles down to the generated voltage wave E1).

The foregoing set of conditions, as shown in Fig. 2, assumes a state of afiairs in which the current is extinguished in both breakers I9, 2| at the first current zero after contact part.

In case the arcs reignite within the breakers [9, 2|, there will occur another half cycle of arcing, as shown in Fig. 3. Consequently, Fig. 3 shows a set of conditions in which the arcs have reignited after the first current zero, there then ensuing another half cycle of arcing- As shown in curve A1, after a slight current zero pause, as at 45, there occurs another half cycle of arcing 46. The oscillatory recovery voltage transient 41 occurs a half cycle later, as indicated in curve C1.

From the foregoing Figs. 2 and 3 it Will be seen that the same conditions reoccur at subsequent current zeros until the arcs within the interrupters I9, 2| are extinguished.

Preferably, the auxiliary breaker 2| and the breaker I9 on test are parts of the same breaker, operating simultaneously. They may, however, be separate interrupters operated independently but substantially simultaneously.

The opening of the auxiliary breaker 2| causes the transformer II! to cease operating as an autotransformer between a high-voltage primary and a low-voltage high-current secondary and to start operating as a reactor in a high-voltage circuit. This changes the circuit containing the breaker I9 on test from a low-voltage high-current circuit to a high-voltage circuit. The recovery transient is that of the high voltage circuit, namely, Ep. It is, of course, recognized that higher voltage recovery rates may be obtained with lower power supply inductance and less capacitance, but these quantities can be measured and taken into consideration in the analysis of data. The transient will be a normal transient for a high voltage circuit.

If the breakers I9, 2| are not ready to interrupt, the arcs will restrike and the short circuit will then be reestablished and will continue until the next current zero.

If only the auxiliary breaker restrikes, the applied voltage on the test breaker I9 is reduced to the lower test voltage and the test in failure of the test breaker. Due to the need for extinction of the auxiliary breaker are as soon as the extinction of the test breaker arc is accomplished, there may be provided a slight diiference in adjustment of the pole units l9, 2! to provide slightly more gap for the auxiliary breaker 21.

It is believed that the testing arrangement of my invention has the following advantages over the existing test circuits of this nature:

1. It functions at current zero and if the arc restrikes functions at the next current zero.

2. It impresses a normal sequence restored voltage across the test breaker l9 and not a restored voltage in the nature of an impulse.

3. The testing arrangement starts the high voltage transient as soon as the arc is extinguished in both breakers I9, 2|. If the arc goes out before a normal current zero, the voltage will rise in the negative direction and on the high voltage recovery transient.

4. There is no delay in impressing the transient upon the arc space.

5. The testing arrangement is very simple. Other systems require a surge generator for each current zero at which they function or will operate at only one current zero.

From the foregoing description of one embodiment of my invention, it will be apparent that I have provided an improved apparatus for testing circuit interrupting devices. The test arrangement is simple and effective. 'It simulates conditions obtained in the field. I have found that results obtained, in the nature of oscillograms of the voltage across the test breaker, utilizing the testing arrangement herein disclosed correspond remarkably well with similar oscillographic results obtained testing breakers out in the field.

Although I have shown and described a specific testing arrangement, it is clearly ,to be understood that the same was merely for the purpose of disclosure, and that changes in modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. Apparatus for testing circuit interrupting devices comprising in combination, an autotransformer, an interrupting device under test connected across the secondary winding of the auto-transformer, means for impressing an alternating voltage across the auto-transformer, an auxiliary interrupting device connected electrically in both the primary and secondary circuits of the auto-transformer, and means for opening the two interrupting devices substantially simultaneously.

2. Apparatus for testing circuit interrupting devices comprising in combination, a testing circuit including an auto-transformer, an interrupting device under test connected across the secondary Winding of the auto-transformer, means for impressing an alternating voltage across the auto-transformer, an auxiliary interrupting device connected electrically in the part of the circuit common to the primary and secondary circuits, an overload relay responsive to the magnitude of the current in the secondary circuit of the auto-transformer, and means responsive to the actuation of the overload relay for substantially simultaneously opening the two interrupting devices.

ROSWELL C. VAN SICKLE'.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,898,752 Wellings et a1. Feb. 21, 1933 2,088,445 Skeats July 27, 1937 2,104,629 Willheim et al. Jan. 4, 1938 2,288,331 Skeats June 30, 1942 2,456,541 Stoecklin Dec. 14, 1948 

